PIR (Passive Infrared) sensors detect infrared radiation emitted by objects, particularly warm bodies like humans and animals. They work by sensing changes in heat within their environment, allowing them to identify movement. This technology is commonly used in security systems, automatic lighting, and energy-saving applications. These sensors are "passive" because they do not emit any energy; instead, they rely on the infrared radiation naturally present in the surroundings. When a warm object moves within the sensor's range, it triggers a response, activating alarms or lights. PIR sensors are popular due to their reliability and low power consumption.